Bird Networks in the Amazon (complexity)
Relationships between organisms are broad
- Competition
- today
- Mutualisms
- jigsaw
- Predation and Consumption
- next week
- Parasites and hosts
- Humans vs other species
- friday data exercise
What is competition?
WHO: Intra vs Inter-specific competition
Competition always results costs to fitness
Intraspecific competition limits population growth
Competition is a powerful driver of evolution
- Natural selection favors individuals that do not compete
- Drives niche differentiation, trait specialization and potentially species diversification
- Directional selection can occur causing character displacement
Gause’s Law: Theory of Competitive Exclusion
- Two species cannot occupy the same niche if they need the same resource
- Species cannot coexist at constant populations
- winner and loser
- Leads to local extinction of weaker competitor or shift to a different ecological niche
Gause’s test tube Paramecium study
Red vs Grey Squirrel in Britain (Murphy 2015)
Competitive exclusion, however, is rare in nature
- Resources are variable/limiting in an environment
- leads to more symmetric competition
- Species compete for multiple resources
- exclusion based on a single resource is too simple
- Complete niche overlap (test tube) is rare
- TAKE HOME: Greater overlap = greater competition
Competition does result in the ‘Realized Niche’
Joseph Connel: Competition among barnacles
Can’t we all just get along?
Co-existence and natural selection
- Overlapping species may evolve to use a niche differently
- resource partitioning = division of resources
- Species whose niches only partly overlap coexist easier
- use the environment differently = niche differentiation
- evolve traits to use different/less overlapping resources = character displacement
- Co-existing species can overlap by using different forms of resources
Co-existence through resource partitioning in lizards
Niche differentiation: different use of microhabitats
Coexistence and character displacement:
